Peter Schiff has a good article that walks through some of the benefits and downfalls of Trump's proposed tax plan.  Cutting the rate for corporations is well publicized, (and last I checked, Trump and his family have a number of corporations); a less well publicized aspect is that many of the wealthiest folks with pass-through incomes will also only pay the 15% rate.  And those who do not have pass-through incomes can legally alter their job structure to be eligible for pass-through treatment.

Pass-through income, by the way, is simply a structure where you have, let's say a LLC, and the income passes through it to the owners, like in a law partnership that operates as a LLC.  The LLC is not taxed the pass-through income as the partners/owners are taxed individually.  But under the Trump plan, they get to enjoy the 15% corporate rate even if they are making millions per year.

This all sounds great if you are the beneficiary, but the real point of Schiff's article is the massive deficits that will occur as most taxes in this country come from the few at the top who will benefit from this new reform - you know, like the billionaires that put it together.  

I highly recommend reading the linked article as I will not summarize it all here.  Let's just say the ultimate cost to the country can be devastating.